Age-related changes in the expression of galanin- and calretinin-like immunoreactivity in the ganglionated plexus of 2-4 day, 6 month and 2 year old guinea-pig gallbladder were investigated. The ganglionated plexus was studied using immunohistochemical labelling techniques on whole mount stretch preparations of the gallbladders. Galanin- and calretinin-like immunoreactivity did not differ significantly between age groups of the 2-4 day and 6 month olds except for some reduction of calretinin-immunofluorescent nerves in the 6 month old preparations. However, in the ganglionated plexus of the 2 year old guinea-pig gallbladders, neither galanin- nor calretinin-like immunoreactivity could be detected. The implication of these findings, in relation to the physiological activity of the gallbladder is discussed.